1. Field of the Invention
The present invention relates to an antireflection film, which has excellent hard coat property, antistatic property, transparency, and scratch resistance and is excellent in alkali resistance; a polarization plate using the antireflection film; and a transmission type liquid crystal display.
2. Description of the Related Art
In general, a display is used under an environment in which natural light or the like enters, regardless of whether used outdoors or indoors. The incident light such as natural light is regularly reflected on a display surface and so on, and a reflected image thus obtained is mixed with a displayed image, whereby a screen display quality is lowered. Thus, it is essential to impart an antireflection function to a display screen and so on, and for the antireflection function, the realization of higher performance and combination with other antireflection functions are required.
In general, the antireflection function is obtained by forming, on a transparent base material, an antireflection layer having a multilayer structure, and more specifically, a repeated structure including high refractive index layers and low refractive index layers which are formed of a transparent material such as metal oxide. Such an antireflection layer having the multilayer structure can be formed by a dry coating method such as a chemical vapor deposition (CVD) method and a physical vapor deposition (PVD) method. As a method for antireflection layer formation, a wet coating method allowing realization of a large area, continuous production, and cost reduction has been proposed.
Such an antireflection layer is sometimes formed on a transparent base material having a relatively soft surface. In this case, in order to impart surface hardness, there has been generally used a method of providing a hard coat layer, constituted of a polymer of an acrylic multifunctional compound, and forming an antireflection layer on the hard coat layer. The hard coat layer has high surface hardness, glossiness, transparency, and scratch resistance according to characteristics of acrylic resin. However, since the hard coat layer has high insulation properties, the hard coat layer is easily chargeable, and there is a problem that a failure occurs due to stains due to adhesion of dust or the like on a surface of a product having the hard coat layer and electrification in a display manufacturing process.
Thus, in an antireflection film having an antireflection layer and a hard coat layer provided on a transparent base material, there have been proposed a method of imparting an antistatic function to the hard coat layer and a method of further providing an antistatic layer between the transparent base material and the hard coat layer or between the antireflection layer and the hard coat layer.
In various image display devices such as a liquid crystal display (LCD), a plasma display panel (PDP), an electroluminescence display (OLED), and a cathode-ray tube (CRT) display device, the antireflection film is installed on a surface of a display to prevent deterioration of contrast due to reflection of natural light and reflection of an image. In particular, in many LCDs, an antireflection film is disposed accompanying realization of a large display screen. In the LCD, a polarization plate is indispensable as an optical material. In general, the polarization plate has a structure in which a polarization layer is protected by two protective films. The antireflection function is imparted to the protective films, making it possible to significantly reduce cost and reduce the thickness of a display device. Meanwhile, when the protective film and a polarization layer are bonded to each other, the protective film is required to have a sufficient adhesiveness to the polarization layer.
The techniques related to the above technique are disclosed in JP-A 11-92750 (KOKAI), JP-A 7-314619 (KOKAI), JP-A 2003-45234 (KOKAI), and JP-A 2005-144858 (KOKAI), for example.